Check out the following thread as preliminary info. You may also need additional equipment such as AUI/Ethernet transcievers, a switch, straight through and/or crossover Category-5 patch cables, and Cisco console kit.

Keep in mind that Ethernet ports (Ethernet interfaces) of any 2500 series router are the AUI ports, NOT the RJ-45 ports. The RJ-45 ports are for CONSOLE and AUX (Auxilary) access which are for totally different situation. This is where the AUI/Ethernet transcievers come in handy.

You may also need the latest IOS and the maximum size of DRAM and flash memory (16/16 MB). It is suggested to always max out the DRAM and flash memory size before installing latest IOS. This way there should be no encounter problem of insufficient memory space.